This invention relates to a syringe barrel and plunger assembly having ellipsoidal configurations. More particularly, the invention relates to a syringe barrel and plunger assembly, whose plane sections are all elliptical, wherein the plunger is equipped with a plunger rod or the assembly is used in a power injector with a built-in plunger rod.
Hypodermic syringes are well-known in the prior art comprising: a cylindrical syringe body, the horizontal cross-section of which is circular, having a fluid-receiving chamber therein; a proximal end; and a distal end. The distal end of the syringe body tapers into a tip having a bore therethrough which communicates with the fluid-receiving chamber. The top is covered by a closure means such as a stopper of a polymeric or elastomeric material, a tip cap or a membrane to prevent leakage and contamination of the fluid medication contained in the syringe barrel.
Some prior art syringes also include a needle assembly with a needle cannula having a proximal end and a distal end and a lumen extending axially therethrough. The proximal end of the needle cannula is engageable with the tip of the syringe barrel. Other prior art syringes include luer collars spaced around the tips of the syringe barrels. The luer collars include threads for engagement with corresponding threads on the proximal ends of the needle cannulas or IV sets equipped with threads.
A plunger is inserted into the open proximal end of the barrel for sliding in fluid-tight engagement with the inside wall of the fluid-receiving chamber. The plunger is equipped with a plunger rod to enable the user to exert pressure on the plunger which results in the sliding movement of the plunger in the proximal or distal directions.
Prior art syringes of all types, i.e. glass, plastic, reusable, disposable and pre-filled are fabricated with a longitudinal cylindrical configuration and a circular transverse configuration. Among the reasons for this configuration is: the familiarity of medical professionals and the general public with this traditional configuration; easy manufacturing process for round, cylindrical barrels including cutting of threads into the tip of barrels, especially glass barrels; and no orientation is required between the plungers and the barrels during assembly.
Syringes and cartridges made of glass or polymeric material for delivery of fluids to and from a patient have been proposed and utilized by the prior art, and have achieved a highly developed state. Various requirements related to specific delivery systems have also been addressed. While specific requirements of fluid delivery to and from a patient may vary, means of delivery remain essentially the same and may be characterized by the following general description of a syringe.
A syringe comprises:
a) a cylindrical barrel having a proximal end designed for receiving a plunger with or without a plunger rod removably attached to the plunger or being integral with the plunger, and a distal end adapted to mount a needle or luer connector thereon; and
b) a plunger slidably mounted in the barrel.
The plunger is inserted into the barrel at the proximal end of the syringe and thus when fluid is contained in the barrel it may be expelled by pushing the plunger in the barrel towards its distal end; or when the syringe is used to withdraw fluid from a patient, the plunger located at the distal end of the barrel is pulled towards the proximal end of the syringe thereby drawing fluid into the barrel. Since a fluid-tight seal is necessary between the plunger and the inside wall of the barrel, a resilient rubber tip is positioned on the distal end of the plunger, or typically, the plunger is made of resilient rubber-like material. Illustrative examples of prior art syringes and cartridges equipped with plunger/plunger rod units include U.S. Pat. Nos. 5,411,489; 5,531,703; 5,979,668 and 5,735,825.
In order to assure air-tight seal between the inside wall of the syringe barrel and the plunger, prior art plungers are manufactured with a larger outside diameter than the inside diameter of the syringe barrels. When the plunger is introduced into the syringe barrel, it is sufficiently compressed to provide adequate pressure between the inside wall of the syringe and the plunger to seal the interface and withstand the challenges of filling, injecting and withdrawing fluids using the syringe without leakage.
In addition to a leakage-proof seal, another requirement in the syringe/plunger combination is the chemical stability of both the syringe and the plunger. While syringes being made of glass or thermoplastic materials are sufficiently chemically inert to pharmaceutical and biological fluids contained therein, the plungers made of natural rubber or butyl rubber have some undesirable properties. The rubber contains additional chemical components such as fillers and accelerators introduced during the curing process which tend to exude to the surface of the plunger during the contact between the plunger and the fluid contained in the syringe. Such exudate is undesirable in an injection or when a biological fluid, such as blood, is withdrawn from a patient for testing purposes. The problem is further aggravated when there is a long-term storage of the content of the pharmaceutical/biological fluid in the syringe. Recognizing the problem of contamination caused by exudates from plungers made of rubber, the prior art has provided plungers made of thermoplastic materials which do not contain the additives that rubber plungers contain. However, thermoplastic materials are not as resilient as rubbers and the seals formed between thermoplastic plungers and the inside walls of syringes tend to be inadequate in some circumstances. Also, over a period of time on storage the thermoplastic plunger may achieve a compression stage wherein the outside diameter of the plunger is reduced thereby no longer capable of forming a tight seal between it and the inside wall of the syringe.
In addition to the tendency of leakage, the thermoplastic plunger does not slide smoothly in the syringe barrel and requires the exertion of excessive force on the plunger rod to move the plunger in the barrel. The exertion of excessive force on the plunger rod may result in uneven delivery of the fluid to the patient or insertion of the needle into a vein or tissue area to an undesirable depth.
In both the rubber and thermoplastic plungers a relatively large compressive force must be exerted on the plungers by the syringe barrel to provide for a tight, leakproof seal. This quality of the seal, however, makes the movement of the plunger difficult. To remedy the problem the prior art used lubricants to reduce friction and drag between the plunger and the inside surface of the syringe barrel. The use of such lubricants, however, is also undesirable with certain parenteral fluids which tend to disperse or dissolve in the parenteral fluids thereby contaminating the parenteral fluids. Attempts to avoid the use of lubricants included the use of various plunger configurations, such as plungers that were provided with one or more ribs projecting forwardly or rearwardly in the barrel to reduce the frictional drag between the plunger and the inside surface of the barrel.
While fluid tightness and sliding property have improved with these attempts, it appears that improvement in one of these properties is not quite achieved without corresponding decrease in the other property: increasing fluid tightness tends to result in decreasing sliding property, while increasing sliding property tends to result in decreasing fluid tightness.
Prior art plungers, variously designated such as sealing cap, plunger head, cup-shaped plunger, cone-shaped plunger and the like, are constructed of elastomeric materials which in the barrel of a syringe or cartridge interface both the content and the inside surface of the barrel.
In the present invention the plunger is constituted by a rigid, non-elastomeric plunger rod tip which interfaces the content of the barrel, and an elastomeric ring which interfaces the inside surface of the barrel.
The prior art has not adequately addressed the ergonomics of large syringes, i.e. the manner of handling the large syringes during repeated injections in the medical arena. The operating forces, such as breakaway and running forces, associated with large syringes can be taxing on the practitioner without using power assisted syringes.
The present invention is directed to syringes and cartridges having a cylindrical longitudinal configuration and an elliptical transverse configuration. The present invention is not directed to syringes and cartridges having a longitudinal cylindrical configuration and a transverse circular configuration.
The advantages of this configuration include: easy handling by gripping the syringe or cartridge barrel across the narrow, flattened section; allows a simple, positive engagement between the plunger and plunger rod so that the plunger is prevented from rotating in either direction and disengaging from the plunger rod; allows uniquely oriented nesting in power injectors; allows improved labeling, i.e., wider area allows label information such as a package insert printed or placed thereon which facilitates reading of the label information; and allows label information to be printed on the back side of the label which can be read through the opposite side of the wide area.
In addition to providing for good ergonomics by the ellipsoidally configured syringe barrel and plunger, the present invention is also directed to the reduction of breakaway and running forces so that the injections or withdrawal process does not strain the practitioner.
In one embodiment of the present invention a self-aligning plunger rod and plunger insert is used in conjunction with the ellipsoidally configured syringe barrel and plunger to direct the external force exerted on the plunger rod in the axial direction.
In accordance with one embodiment of the present invention, there is provided a syringe or cartridge barrel (hereinafter sometimes referred to as barrel denoting either or both the syringe barrel or the cartridge barrel) in combination with a plunger or plunger and rod assembly for receiving a medical fluid from a site or for expelling a medical fluid contained in the syringe or cartridge barrel to a site. The medical fluid can be a biological fluid, such as blood, or pharmaceutical fluid such as a diagnostic medium, and a nutritional preparation. The syringe or cartridge barrel and plunger combination comprises:
(a) a barrel of ellipsoidal configuration of glass or polymeric material having an inner surface defining an ellipsoidal chamber for retaining a medical fluid therein, said barrel having:
(1) a distal end terminating in a tapered tip having a bore therethrough to which an injection needle or a connector equipped with a tubing conduit can be attached; and
(2) a proximal end for slideably receiving a plunger of ellipsoidal configuration;
(b) a plunger rod having a stem portion and an ellipsoidal head portion which are integral with each other, said head portion being of a rigid, non-elastomeric material, preferably a thermoplastic material, having a distal end, a proximal end, and a generally ellipsoidal shaft therebetween, said ellipsoidal shaft comprising:
(1) a tip at the distal end thereof adapted for interfacing a medical fluid contained in the ellipsoidal chamber of said syringe barrel; and
(2) an exterior surface comprising a groove adapted to receive an elastomeric ring;
(c) an elastomeric ring of ellipsoidal configuration having an inside wall and an outside wall, said inside wall defining a vacant ellipsoidal center, said elastomeric ring being positioned on the exterior surface of the ellipsoidal shaft without covering the tip of the plunger rod head comprising:
(1) a protuberance on the inside wall thereof engaging the groove in the ellipsoidal shaft to form a non-slideable seal therewith; and
(2) a plurality of rims on the outside wall of the elastomeric ring for interfacing the inner surface of said ellipsoidal barrel to provide a slideable seal between said plunger and said barrel.
The syringe or cartridge barrel preferably also includes a flange of ellipsoidal or hexagonal configuration at its proximal end.
In another embodiment of the present invention the stem portion and the head portion of the plunger rod are separate elements, and accordingly, the syringe or cartridge barrel and plunger combination comprises:
(a) a barrel of ellipsoidal configuration of glass or polymeric material having an inner surface defining an ellipsoidal chamber for retaining a medical fluid therein, said barrel having:
(1) a distal end terminating in a tapered tip having a bore therethrough to which an injection needle or a connector equipped with a tubing conduit can be attached; and
(2) a proximal end for slideably receiving a plunger of ellipsoidal configuration;
(b) a plunger rod head of ellipsoidal configuration, said plunger rod head being of a rigid, non-elastomeric material, preferably a thermoplastic material, having a distal end, a proximal end, and a generally ellipsoidal shaft therebetween, said ellipsoidal shaft comprising:
(1) a tip at the distal end thereof adapted for interfacing a medical fluid contained in the ellipsoidal chamber of said syringe barrel;
(2) an ellipsoidal inner chamber at the proximal end thereof, said ellipsoidal inner chamber having female spiral threads therein for engaging spiral male threads of a plunger rod stem;
(3) an exterior surface comprising a groove or recess therein adapted to receive an elastomeric ring having a protuberance thereon;
(c) an elastomeric ring of ellipsoidal configuration having an inside wall and an outside wall, said inside wall defining a vacant ellipsoidal center, said elastomeric ring being positioned on the exterior surface of the ellipsoidal shaft of the plunger rod head, without covering the tip of the plunger rod head, comprising:
(1) a protuberance on the inside wall thereof engaging said groove or recess in the ellipsoidal shafts of the plunger rod head to form a non-slideable seal therewith; and
(2) a plurality of rims on the outside wall of the elastomeric ring for interfacing the inner surface of the barrel to provide a slideable seal between the plunger and the barrel;
(d) a plunger rod stem having a distal end and a proximal end comprising:
(1) spiral male threads on the distal end thereof for engaging the spiral female threads in the ellipsoidal inner chamber of the plunger rod head; and
(2) a thumb rest on the proximal end onto which external pressure is applied for injecting a medical fluid into a site or withdrawing a medical fluid from a site in operating the syringe.
In another embodiment of the present invention, a syringe or cartridge barrel and plunger combination includes a self-aligning plunger rod and plunger insert assembly for manual or power-assisted withdrawal of a medical fluid from a site or for expelling a medical fluid from the barrel. The combination comprises:
(a) an ellipsoidal barrel;
(b) a self-aligning plunger rod;
(c) an ellipsoidal non-elastomeric plunger insert; and
(d) an ellipsoidal plunger ring.
The plunger rod and plunger insert assembly has a self-aligning feature wherein the plunger rod tip fits into the socket of the plunger insert and freely glides therein. This feature allows the plunger rod tip to float in the socket of the plastic plunger insert and eliminates lateral pressure on the plastic plunger insert.
(a) The ellipsoidal barrel comprises:
an ellipsoidal body of glass or polymeric material having an inner surface defining an ellipsoidal chamber for retaining a medical fluid therein, said ellipsoidal body having:
a distal end terminating in a tapered tip having a bore therethrough to which an injection needle or a connector equipped with a tubing conduit can be attached; and
a proximal end for slideably receiving a plunger of ellipsoidal configuration.
(b) The self-aligning plunger rod having a distal end and a proximal end comprises:
an end disc at said distal end;
a plunger rod tip extending from said end disc adapted to engage a non-elastomeric plastic plunger insert, said plunger rod tip comprising:
a neck portion; and
a ball portion having slots therein extending axially from said neck portion;
a thumb rest at the proximal end of the self-aligning plunger rod for facilitating exertion of an external pressure on said plunger rod.
(c) The ellipsoidal non-elastomeric plunger insert comprising:
an ellipsoidal shaft having a distal end and a proximal end;
at least one ellipsoidal recess between the distal end and the proximal end adapted to hold an elastomeric plunger ring having an ellipsoidal protuberance to engage said ellipsoidal recess;
a cone-shaped head, having an inside surface and an outside surface, extending from the distal end of said ellipsoidal shaft;
an ellipsoidal flange extending from the proximal end of said ellipsoidal shaft;
a first ellipsoidal rim constituting an underside of said ellipsoidal flange;
a second ellipsoidal rim adjacent to said first ellipsoidal rim and projecting slightly above a horizontal surface of said first ellipsoidal rim;
a cavity defined within said second ellipsoidal rim and the inside surface of the cone-shaped head;
a plurality of tabs extending from the second ellipsoidal rim into said cavity; and
notches between said tabs to receive said slotted ball portion of said plunger rod tip.
(d) The ellipsoidal plunger ring having an inside wall and an outside wall, said inside wall defining a vacant ellipsoidal center, said inside wall having an ellipsoidal protuberance thereon for engaging said ellipsoidal recess in the non-elastomeric plastic plunger insert; and a plurality of rims on the outside wall for interfacing the inner surface of said ellipsoidal barrel to provide a slideable seal between said ellipsoidal plunger ring and the inside surface of said ellipsoidal barrel.
The syringe or cartridge barrel and plunger combination of the present invention can be used manually or with a power injector.